Electrohydraulic Emergency Circuit for Manipulator Mast Control
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Solution Overview
Problem
Existing electrohydraulic control circuits for manipulators, such as truck-mounted concrete pumps, face challenges in safe and intuitive emergency operation when normal control components fail, including delayed response due to long hydraulic lines and the need for separate control oil circuits, which complicates control and increases weight.
Innovation Solution
An electrohydraulic control circuit with an emergency operating unit that allows electrical control of emergency valves, featuring a stepper motor-controlled proportional valve arranged directly on the drive unit, reducing hydraulic lines and enabling faster response, and a local control device for precise motor control, along with a separate emergency pressure supply unit for fault-tolerant operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If proportional valves are arranged in a central control block away from drive units, then control is centralized, but response time is delayed due to long hydraulic lines
Solution Approach 1:
The control system is segmented into decentralized control units, with each drive unit having its own proportional valve integrated directly on it. This segmentation eliminates long hydraulic lines between central control block and drive units, enabling immediate response when emergency operation is activated.
Solution Approach 2:
A common return line serves as an intermediary element that allows both normal operation and emergency operation to share hydraulic infrastructure. This mediator enables the emergency valve to drain hydraulic oil from the drive unit chamber back to the tank through the shared return line, providing a simple and reliable emergency function without requiring separate complex infrastructure.
2Reliability
If lowering brake valves are used to prevent manipulator lowering in event of damage, then safety is improved, but response behavior is greatly delayed
Solution Approach 1:
The lowering brake valve function is extracted and replaced by check valves with significantly faster control behavior. The check valves are positioned directly on the drive units with minimal hydraulic line length, eliminating the delayed response characteristic of centralized lowering brake valves while maintaining the safety function of preventing uncontrolled lowering.
Solution Approach 2:
The mechanical lowering brake valve system is replaced with a simpler check valve mechanism that provides faster response. The check valves allow free flow in the normal direction but prevent reverse flow, providing passive safety without the complex mechanical braking mechanism and its associated response delays.
3Ease of operation
If a separate control oil circuit is provided for opening/closing check valves and supplying proportional valve, then valve control is enabled, but additional pressure supply line and tank line are required
Solution Approach 1:
The main pressure supply line and tank line are designed to serve multiple functions: normal operation of proportional valves, emergency operation of emergency valves, and control of check valves. This multi-functionality eliminates the need for separate control oil circuits, reducing the number of hydraulic lines while maintaining full valve control capability.
Solution Approach 2:
Separate control oil circuits for check valves and proportional valves are merged into a single unified hydraulic system. The same pressure supply line and tank line that serve normal operation also provide control pressure for all valve operations, including emergency functions, thereby simplifying the overall hydraulic architecture.
4Device complexity
If a common return line is used for normal operation and emergency operation, then system simplicity is improved, but emergency operation becomes impossible in event of leak
Solution Approach 1:
The emergency valve is positioned directly on each drive unit with local control capability, creating a localized emergency response system. This local quality ensures that even if the common return line has a leak elsewhere in the system, the emergency valve can still drain hydraulic oil from its associated drive unit chamber through the intact local section of the return line, maintaining emergency operation capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures safe and intuitive emergency operation with reduced weight and complexity, enabling reliable control of manipulator mast segments even in failure scenarios, with improved response behavior and weight savings.
Implementation Method 1
The proportional valve can be controlled with a stepper motor (31)
Implementation Method 2
electrically controlled proportional valve (28)
Implementation Method 3
hydraulically actuated drive units (2)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to an electrohydraulic control circuit (1) for actuating a hydraulically actuated drive assembly (2, 2a, 2b, 2c, 2d), by means of which the orientation of a mast segment (3, 3a, 3b, 3c, 3d) of a manipulator (4), in particular of a large manipulator for truck-mounted concrete pumps, can be adjusted, having an electrically actuated proportional valve (28) which is connected to hydraulic operating lines (29, 30) of the drive assembly (2, 2a, 2b, 2c, 2d) in order to actuate it during normal operation, wherein the proportional valve (28) is connected to a pressure supply line (24) and to a return line (25), wherein, for emergency operation, an emergency valve (36) is connected to the hydraulic operating lines (29, 30) of the drive assembly (2, 2a, 2b, 2c, 2d) in order to actuate it during emergency operation. It is an object of the invention to specify a control circuit and a manipulator which makes reliable emergency operation possible in the event of the failure of the regular control circuit components. To this end, the invention proposes that, in emergency operation, the emergency valve (36) is actuated via an emergency operating unit (56). As an alternative or in addition to this, the emergency valve (36) can be connected to a further pressure supply line (26) which is connected to an emergency pressure supply unit (8), and as an alternative or in addition, furthermore, the emergency valve (36) can be connected to a further return line. Moreover, the invention relates to a manipulator (4), in particular a large manipulator for truck-mounted concrete pumps.